Sprinkler base



FIG. 1 is a top plan view of a sprinkler base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevation view thereof; and

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a top perspective view thereof. 

The ornamental design for a sprinkler base, substantially as shown and described. 